From 25f70a5abbc2e3e38b8a67013f91c1ccea961aaa Mon Sep 17 00:00:00 2001
From: Yueh-Hsuan Chiang <yhchiang@fb.com>
Date: Tue, 16 Dec 2014 17:10:23 -0800
Subject: [PATCH] Avoid unnecessary unlock and lock mutex when notifying
 events.

Summary: Avoid unnecessary unlock and lock mutex when notifying events.

Test Plan: ./listener_test

Reviewers: igor

Reviewed By: igor

Subscribers: sdong, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D30267
---
 db/db_impl.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/db/db_impl.cc b/db/db_impl.cc
index a87d4d1476..3275165e88 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -1112,6 +1112,9 @@ Status DBImpl::FlushMemTableToOutputFile(
 void DBImpl::NotifyOnFlushCompleted(
     ColumnFamilyData* cfd, uint64_t file_number,
     const MutableCFOptions& mutable_cf_options) {
+  if (cfd->ioptions()->listeners.size() == 0U) {
+    return;
+  }
   mutex_.AssertHeld();
   if (shutting_down_.load(std::memory_order_acquire)) {
     return;